A contract made between Britain and Spain in 1713 for the sale of slaves to the Spanish American colonies. In the Peace of Utrecht (1713) Spain granted Britain a monopoly of the supply of slaves to the Spanish American colonies of 144,000 slaves at 4,800 a year for thirty years, with other privileges. They were the origin of the speculation that resulted in the South Sea Bubble and led to endless disputes, including the War of Jenkins’s Ear between England and Spain in 1739. The treaty was ended by agreement in 1750.